Method of reinforcing cores, utilizing glass tubes



y 3, 1956 J- F. HURLEY 2,752,652

METHOD OF REINFORCING CORES, UTILIZING GLASS TUBES Filed Sept. 28, 1954 I N V EN TOR. Jomv F #047 by Y E B [a /0 E 7 7770 ell M METHOD OF REINFORCIN G CORES, UTILIZING GLASS TUBES John F. Hurley, Solon, Ohio, assignor to Central States Industrial Supply Company, Cleveland, Ohio, a corporation of Ohio Application September 28, 1954, Serial No. 458,739 8 Claims. (Cl. 22-172) This invention is concerned with improvements in and relating to foundry cores, and more particularly to improvements in foundry cores which must be structurally reinforced so that they may not be readily broken before or after baking, or while being positioned in a mold and during the pouring of the metal. These, therefore, are the general objects of the present invention.

Heretofore it has been common practice to imbed metal rods or tubes within foundry cores to provide the reinforcement requirement to prevent breakage of the cores to vent the core during the curing of the core. The removal of such metal reinforced cores from the casting is difiicult due to the rigidity of the cores. Reinforced cores are a material item in the cost of making the castings for which they are used. Because of this cost, it has been common practice to reclaim the metallic rods or tubes, by removing them from the foundry sand, following the removal of the cores from the castings. The reclaimed rods or tubes generally are warped and require straightening before they may be used again. Thus reclaimed it is sometimes possible to use one rod or tube several times. While reclaiming the rods and tubes reduces the expense involved, it is nevertheless true that the reclaiming operation is costly.

For some time it has been more or less common prac tice to bake or cure foundry cores in gas ovens or by inductive or similar electric heating processes. Such processes have many advantages, all of which are well known in the trade. However, the use of inductive or electric processes has been more or less confined to cores which required no reinforcement or venting by rods or tubes. This is due to the fact that the introduction of such cores in an induction or similar oven without interference by the rods or tubes with the paths of electrical forces is difficult and generally considered impractical. This is particuiarly true in connection .with large cores, such as those used for casting automotive engine blocks and similar castings. Accordingly, a more specific object of'the present invention is the provision of a reinforced or vented foundry core which may be manufactured with a mini mum of expense, and which may be baked or cured in induction or similar electric ovens.

The present invention contemplates the reinforcement of a foundry core with a glass rod or tube. The cost of glass tubes, when compared with the cost of the metal tubes used in the past, is such that the former are expendable and need not be reclaimed, being frangible they permit the core to be readily removed from the casting, and when completely crushed they may remain in the core sand, which is generally reclaimed. Being made of glass, the coefficient of expansion and contraction of the tubes closely parallels that of silica sand which is the base of most core compounds. Further cores reinforced by glass tubes may be placed in induction and similar electric furnaces without causing interference with the paths of the electrical forces therein. These, therefore, are some of the advantages of the present invention.

Other objects and advantages of the invention will be nited States Patent O come more apparent from the following description of an embodiment thereof which is illustrated in the accompanying drawings, in which Fig. 1 is a sectional view through a core box illustrating the improved glass reinforcement tube in position;

Fig. 2 is a view similar to Fig. 1 showing the core box after it has been filled with the core forming material;

Fig. 3 is a transverse section, the plane of which is indicated by the lines 33 of Fig. 2;

Fig. 4 is a section taken through the completed core;

Fig. 5 is an enlarged sectional View through the reinforcing tube and its supporting mandrel; and

Fig. 6 is a view similar to Fig. 5 but illustrating a modified form of tube support. I

Referring to the drawings, it will be seen that the invention has been illustrated in connection with the making of a core adapted for use in the manufacture of automotive engine blocks, and in which one or more cylinders and a transverse portion of the crank case are formed by a single core. Cores of this type are in general use at the present time and are exemplary of cores which require reinforcement or venting to prevent cracking or breaking of the core before or after baking, while in storage, while being placed in position in a mold, or during the pouring of the metal to form the casing. The core is formed on a base 10 on which an inverted open ended core box 11 is positioned. For casting engine blocks the core box generally is provided with one or more cylinder forming portions comprising vertically extending cylindrical openings or chambers 14, the bottoms of which are closed by the base 10. An enlarged single crank case shaped cavity 15 surmounts the chambers 14.

Cores for engine blocks must be free from cracks and the cylinder forming portions 26 thereof must align accurately with each other and extend vertically from the crank case forming portions 27. The tendency of the core to break and warp is greatest at the junction of the pottions 26 with the portions 27. Accordingly, the core must be reinforced to maintain such alignment and prevent breakage or cracking. To reinforce the core, the present invention contemplates the imbedding glass tubes 16 in the core, there being one tube axially aligned with each cylinder formation 26 of the core. The tubes are open ended and are so imbedded that they extend axially of the cylinder formations with their lower faces in the plane of the upper surface of the base 10 and with their upper ends extending through the cylinder forming cavities 14 into the crank case forming cavity 15 and terminating substantially midway between the top and bot tom of the latter.

The reinforcing tubes 16 are supported by mandrels 17. The mandrel shown in Figs. 1 to 5 inclusive comprises a tapered steel rod having a threaded base portion 18, by means of which it is secured in position to the base 10. The diameter of the mandrel is smaller than the internal diameter of the tube. The lower end of the mandrel is encircled by a resilient bushing 20 made of rubber or rubber-like material. The diameter of the bushing is such as will provide a relative snug fit between its external wall of the tube, and the mandrel is of such height as will support the tube and yet permit rapid positioning thereof. To facilitate the positioning of the glass tube on the mandrel, without breakage of the tube, the upper end of the bushing may be tapered as at 21. The bushing 20 is provided with a peripheral base flange 22 on which the lower face of the tube rests and which seats in a recess 23 formed in the base 10 with its upper surface substantially flush with the upper surface of the base.

Fig. 6 illustrates a modified form of support or mandrel in which the entire mandrel 17 is covered with a coating 25 of rubber or rubber-like material. In this instance,

the bushing 20 and its flange 22 is formed integral with the coating.

Following the positioning of the glass reinforcing tubes 16 on their mandrels 17, the base and the core box 11 are placed as a unit in a core forming machine. Such machines are well known at the present time so they will not be described in detail herein. Sufilce it to say they generally direct granular core sand and thermo binding material into the open upper end 29 of the core box by means of a blast of air of considerable force to insure compacting of the material. During this operation, the bushing 20 and its flange 22 provide a resilient support for the glass reinforcing tube 16 protecting it against breakage.

After the core material has been compacted, the core box 11 is inverted and placed on a platen 12. The base 10 together with the tube mandrels 17 are removed, leaving the glass reinforcing rod in position in the core. The core box 11 is then removed and the core is baked or cured in an oven in the usual manner.

The wall thickness of the glass tubes is such as will provide suflicient vertical and transverse strength to withstand the strains encountered during the positioning and compacting of the core material. Such tubes are relatively light in weight and are relatively inexpensive. Indeed it has been found that they are much less expensive than the cost of reclaiming metallic tubes. Further such tubes are capable of withstanding the baking or curing temperatures without warping. Likewise, being made entirely of glass they have substantially the same coeflicient of expansion and contraction during the baking and subsequent cooling operations of the silica sands which form the base of the core material. This together with the fact that glass has an aflinity for silica sands when subjected to heat not only prevents separation of the core material from the tube during the curing and cooling operations, but also actually increases the adhesion between the two. The glass tube also transmits heat at a rate parallel with that of the core material and thereby assists in the curing of the core. Being non-metallic, the glass reinforcing tube does not interfere with curing of the core by electric induction or similar methods.

The tube having both ends open serves as a core vent during the core curing and casting operations, and if desired may be provided with minute radially extending vent openings. Generally, it has been found that by leaving the imbedded upper end of the tube open, no other vent orifice is required.

Furthermore, while glass tubes are rigid and of suflicient strength to enable filling and compacting of the core by the usual core blowing methods, they nevertheless are frangible and may be readily broken to facilitate the removal of the core from the completed casting.

While the bushing 20 has been described as being made of rubber, it is to be understood that the term includes, rubber substitutes and synthetic rubbers, having similar physical properties.

I claim:

1. The method of forming a sand core of a shape requiring reinforcement, comprising positioning a resilient flanged bushing in a core box, positioning an elongated open ended glass tube in a vertical position in the core box with one end thereof encircling said bushing and the face of such end resting on such flange, filling the core box with compacted sand, removing the core box and bushing from the compacted core leaving the tube imbedded therein, and thereafter curing the core by a baking operation.

2. The method of forming asand core requiring internal reinforcement, comprising securing to the core box a rod supporting member having rubber supporting faces, placing a vertically extending open ended glass tube in said core box with one end thereof supported by said rubber faces, filling the core box with both core sand and a thermo binding material while compacting such sand and material, stripping the core box and rod supporting member from the compacted core leaving the glass tube imbedded therein, thereafter curing the core by a baking operation.

3. A device for supporting a reinforcing tube in a core box, comprising a rigid pin adapted to be secured to a core box and of a diameter less than the internal diameter of the reinforcing tube, and adapted to project vertically into the tube, and a resilient member encircling the pin and on which the end of the tube may rest.

4. A device for supporting a glass reinforcing tube in a core box comprising a base, a metallic pin secured to said base and adapted to telescopically receive said tube, said pin having an external diameter less than the internal diameter of the tube, a rubber bushing encircling the base of the pin and adapted to provide a snug fit with the lower end of the tube, said bushing having an integral flange adapted to supportingly coact with the lower face of the tube.

5. A device for supporting an open ended core reinforcing tube in a core box, comprising a rigid pin adapted to be secured to a core box and of a diameter less than the internal diameter of the tube and on which the tube may be telescopically positioned, and a resilient bushing member encircling the secured end of the pin and snugly fit into the lower end of the tube, and resilient means to supportingly coact with the lower face of the tube.

6. A device for supporting an open ended glass reinforcing tube in a core box comprising a base, a metallic pin secured to said base and adapted to telescopically receive said tube having a rubber coating, and having an external diameter less than the internal diameter of the tube.

7. A baked sand core for making hollow metal castings, said core having a non-metallic frangible tube imbedded therein, and wherein one end of said tube is open ended and terminates Within the core.

8. A core according to claim 7 wherein the other end of the core terminates at an external surface of the core.

Dietert: Foundry Core Practice, 1950, Chapters Ill and IV.

The Iron Age, April 12, 1951, pages 107-109. 

3. A DEVICE FOR SUPPORTING A REINFORCING TUBE IN A CORE BOX, COMPRISING A RIGID PIN ADAPTED TO BE SECURED TO A CORE BOX AND OF A DIAMETER LESS THAN THE INTERNAL DIAMETER OF THE REINFORCING TUBE, AND ADAPTED TO PROJECT VERTICALLY INTO THE TUBE, AND A RESILIENT MEMBER ENCIRCLING THE PIN AND ON WHICH THE END OF THE TUBE MAY REST. 